A video apparently showing one of five Britons who have been held in Iraq since a brazen daylight abduction in May was broadcast by al-Arabiya television station today.

In the video, seemingly filmed in November, kidnappers issued a demand that UK troops return home within 10 days or they would kill one of their hostages as a “first warning”.

The five civilians were kidnapped from the Iraqi Finance Ministry in Baghdad six months ago. They are believed to be four security guards who were working for a private firm and a financial expert who was advising the Iraqi government.

Downing Street criticised the airing of the video. “We have seen the media broadcast of the footage. We condemn the publication of this video, which serves only to add to the distress of the men’s families and friends," the Prime Minister's spokesman said.

“It’s our long-established policy not to comment on such footage, and we encourage others not to speculate. That would be unhelpful and distressing to the families concerned.”

The hostage shown in the clip is sitting on the floor in front of an Arabic banner reading “the Islamic Shiite Resistance in Iraq” - he is flanked by masked gunmen pointing assault rifles at him.

In a clear English accent, he said: “My name is Jason. Today is November 18. I have been here now 173 days and I feel we’ve been forgotten.”

The abductors accused the UK of plundering Iraq’s wealth and claimed that the hostages confessed they had come to Baghdad to loot the country’s resources.

A British Foreign Office spokesman confirmed that the video had been shown at about 12.40pm today on the Dubai-based network.

“No matter what the cause, hostage taking can never be justified. We again call on those holding the men to release them unconditionally,” he said.

At the time of the kidnapping Iraqi officials blamed al-Mahdi Army, the militia controlled by the radical Shia cleric Muqtada al-Sadr.

It was believed to have been a retaliatory attack after British soldiers killed the militia’s commander in Basra a week earlier. But al-Sadr’s followers have denied responsibility and suspicion has since fallen on al-Mahdi Army splinter groups, some of which the US believes are controlled by Iran.

The abduction of the British men sent shockwaves through foreign workers stationed in Iraq. Up until that point contractors had been relatively safe once inside government buildings in Baghdad.

The kidnappers had strolled up to the guards on duty at the Finance Ministry and were reportedly allowed inside after politely explaining that they were with the Commission on Public Integrity, an anti-graft agency.

The men dressed in police uniforms had sealed off Palestine Street near the heavily fortified Green Zone. Witnesses suggested there was little or no violence involved, before the kidnappers left with the Britons.

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